Thinker Toolbox is a collection of 19 free, browser-based utilities that actually work. No sign-ups, no subscriptions, no data harvesting. Just tools that do what they say on the tin.
We got fed up with word puzzle solvers that are buried under clutter, colour pickers that want your email, and tip calculators that track your dinner bills. So we built our own. Then we put them all in one place, made them work offline, and called it Thinker Toolbox.
The name used to be a bit misleading — but Thinker Toolbox covers it. Finance calculators, solar & energy tools, date calculators, word puzzles, and everyday utilities. Tools for thinkers, all in one toolbox.
Mortgage Calculator
Monthly payments, amortization, overpayment savings, stamp duty & affordability checker.
Salary Calculator
UK take-home pay with tax, NI, student loans & pension deductions.
Pension Calculator
Retirement projections, state pension age & drawdown vs annuity.
Loan Calculator
Personal loans, car finance (HP & PCP), credit card payoff & amortization.
Savings Calculator
Compound interest, goal-based savings & inflation-adjusted returns.
Percentage Calculator
Percentage of a number, increase/decrease, reverse % & VAT.
Solar Calculator
Solar panel savings, ROI & payback with or without battery storage.
SEG Earnings
Compare Smart Export Guarantee rates & maximise your solar export income.
Octopus Tariff Compare
Find the best Octopus Energy tariff for solar panels & battery storage.
Battery Optimiser
Optimal charge & discharge strategy for your home battery on any tariff.
Date Calculator
Days between dates, age calculator, add/subtract days & UK bank holidays.
Tip Calculator
Calculate tips and split bills between friends.
Cooking Converter
Convert measurements, scale recipes & reference ingredient densities.
Sudoku Solver
Solve 4×4, 9×9 & 16×16 Sudoku puzzles instantly.
Colour Picker
Generate harmonious palettes with WCAG contrast checking.
Crossword Solver
Find words matching a pattern. Use ? for unknown letters.
Anagram Solver
Unscramble letters to find all valid words.
Wordle Solver
Get optimal guesses for your daily Wordle.
Scrabble Finder
Find highest-scoring words from your rack.
Works offline. Once you've visited, the tools cache themselves in your browser. No internet? No problem. On the train, in a café, in a dead zone — they still work.
Works on your phone. Every tool is designed mobile-first. Big buttons, readable text, no pinching and zooming.
Fast. No server round-trips for calculations. Everything runs in your browser. The word puzzles load a 168,000-word dictionary instantly. Finance calculators export to PDF on demand.
Private. This site may use cookies for analytics. You can accept or reject these in the cookie banner. Your calculator inputs stay in your browser and are never sent anywhere. PDF reports are generated locally — nothing leaves your device.
No accounts. No sign-up, no email, no password. Just open and use.
The calculators on this site are for illustration purposes only and do not constitute financial advice.
Mortgage payments, savings projections, and other financial calculations are estimates based on the figures you provide. Actual amounts may vary depending on your lender's terms, interest rate changes, fees, and other factors not captured by these tools.
Always consult a qualified financial adviser before making important financial decisions. Do not rely solely on these calculators when considering mortgages, loans, savings, or investments.
The dictionary used in the word puzzle tools is the ENABLE word list (Public Domain), containing over 168,000 Scrabble-valid words. It also includes the official Wordle answer list for the Wordle Solver.
It's great for casual use, but if you're training for competitive Scrabble, you should note that a small number of words added in later Scrabble dictionary updates (such as QI and ZA) are not included in the ENABLE list.
Made with ♥ by a ragtag bunch who got tired of tools that don't just work.
Got feedback, found a bug, or got an idea for a new tool? We'd love to hear from you.
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